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Looking at the images of AOA sensor it seems like there is no space for some insects to creep in and do the damage.

Considering more than 1 sensor has failed probably they will have to look at the instrument itself in terms of failure rate and redesign it to make it less failure prone .....Some one has to do a long hard look at these sensors including pitot tube and make it fail proof.

To my view it is more of a case of equipment failure or related sensors that these equipment pass on the inforamation too.

One quick thing that comes to my mind is to have 2 Additional AOA and Pitot Sensors which does not remain exposed constantly as external device but remains internal which pilot can activate it if primary sensor fails probably independent of the primary sensor but integrated with FCS , So that would reduce the constant exposure these sensors have left to some extreme environment.

AOA and Pitot Tube failure even though these are relatively simple instruments has lead to crash of many aircraft but all they did was add more in numbers instead of looking at some alternate solution.

people on airliners.net forum are veering around to pov that while MCAS may have contributed in some way to ethiopia crash, there is some deeper bug in the system perhaps in the autopilot + navigation sensors.

Design decision of MCAS acting like a 'third pilot' with ability to give commands to flight computer to move the control surfaces, overriding the pilot is interesting. Looks like they will have to go thru many iterations before validating this combination. Situation similar to fly by wire A320 in the nineties.

Me thinks MCAS was just poor patch work to fix fundamental hardware design flaw in terms of change of CG due to Engine placement by introducing a Sofware Fix , They just PRed it to lets make a Safe Aircraft More Safer but it turned out to be just the opposite.

To make matter worse they wanted to hide this poor patch work by not letting the pilot know it exist since it was suppose to do its job in a automated discrete way.

Little did Boeing realise this would turn into a nemesis taking life of more than 250 pax and pilot/crew.

arvin wrote:Design decision of MCAS acting like a 'third pilot' with ability to give commands to flight computer to move the control surfaces, overriding the pilot is interesting. Looks like they will have to go thru many iterations before validating this combination. Situation similar to fly by wire A320 in the nineties.

well they did say AI would change the world. right now AI is unable to navigate a car to the extent of driving in crowded mixed desi traffic ...

3 dehavilland comets had disintegrated in mid air, kia all on board including one over India in 1953!!

The 737 itself had 2 crashes and one near crash where the aircraft went into a scary dive before the pilot managed to recover, back in the early 90's. This was due to the infamous rudder control module issue, which caused a rudder hardover and sent the aircraft suddenly plunging straight to the ground. It was only after the third incident that they found the issue and fixed it.

Ethiopian Airlines #ET302 flight recorders sent to France for investigation by Bureau d'Enquêtes et d'Analyses (BEA). They are a leader in crash investigations. Both recorders have been severely damaged. Photo of the flight data recorder has been released by investigators.

Austin wrote:Looking at the images of AOA sensor it seems like there is no space for some insects to creep in and do the damage.

Considering more than 1 sensor has failed probably they will have to look at the instrument itself in terms of failure rate and redesign it to make it less failure prone .....Some one has to do a long hard look at these sensors including pitot tube and make it fail proof.

To my view it is more of a case of equipment failure or related sensors that these equipment pass on the inforamation too.

One quick thing that comes to my mind is to have 2 Additional AOA and Pitot Sensors which does not remain exposed constantly as external device but remains internal which pilot can activate it if primary sensor fails probably independent of the primary sensor but integrated with FCS , So that would reduce the constant exposure these sensors have left to some extreme environment.

AOA and Pitot Tube failure even though these are relatively simple instruments has lead to crash of many aircraft but all they did was add more in numbers instead of looking at some alternate solution.

srin wrote:Pitot tube blockage due to icing seems dependent not just on latitudes but on weather at high altitudes.

In one of the Air France Air Crash investigation which happened due to Pitot Tube Icing and Pilot taking wrong action which lead to crash.

It was mentioned in at High Altitude depending on weather condition the Pitot tube do freeze and Air craft can show incorrect speed , Pilots are advised to stay calm and do nothing and wait for time to pass till the Pitot tube defrezes and returns to normal. The Auto Pilot though gets disengaged and pilot has to take manual control

Latest reports on the Ethiopian crash suggest that the aircraft was flying unusually fast even though it was less than five minutes into the flight. Its high speed was unsafe at its low altitude and air traffic controllers were wondering what was going on even before the pilot informed them of a flight control issue and requested to return to the airport. Reasons for its fluctuating altitude could be the MCAS problem as earlier but I have no idea why it would overspeed so quickly into the flight.

My speculation is it's all related if someone builds a system that is supposed to prevent AC from going into a stall then it is highly likely they don't do so by just controlling pitch but even airspeed among other variables . May be pilot pulled up soon after takeoff and system tried to inject speed to prevent what it read was a near stall condition and pilot found it odd for he might be used to pulling such manoeuvres on an AC that does not have a system that overcompensates so much.

srin wrote:Pitot tube blockage due to icing seems dependent not just on latitudes but on weather at high altitudes.

In one of the Air France Air Crash investigation which happened due to Pitot Tube Icing and Pilot taking wrong action which lead to crash.

It was mentioned in at High Altitude depending on weather condition the Pitot tube do freeze and Air craft can show incorrect speed , Pilots are advised to stay calm and do nothing and wait for time to pass till the Pitot tube defrezes and returns to normal. The Auto Pilot though gets disengaged and pilot has to take manual control

nachiket wrote:Latest reports on the Ethiopian crash suggest that the aircraft was flying unusually fast even though it was less than five minutes into the flight. Its high speed was unsafe at its low altitude and air traffic controllers were wondering what was going on even before the pilot informed them of a flight control issue and requested to return to the airport. Reasons for its fluctuating altitude could be the MCAS problem as earlier but I have no idea why it would overspeed so quickly into the flight.

the speed was within acceptable limits.

overspeed implies/indicates that a critical flight parameter was exceeded placing the aircraft in imminent danger.

negi wrote:My speculation is it's all related if someone builds a system that is supposed to prevent AC from going into a stall then it is highly likely they don't do so by just controlling pitch but even airspeed among other variables . May be pilot pulled up soon after takeoff and system tried to inject speed to prevent what it read was a near stall condition and pilot found it odd for he might be used to pulling such manoeuvres on an AC that does not have a system that overcompensates so much.

After binge-watching nearly 18 seasons of Aircrash investigations (and I'm watching season 19 now), I've seen stalls due to:- icing on the wings - de-icing lowering engine thrust which stalled the aircraft- pilot losing situational awareness and holding nose up instead of down (pitot tube showing crazy airspeed readings)- pilot not noticing that the autopilot disengaged inadvertently and the plane is in a deep bank- pilot mistakenly switching off the working engine instead of the non-working one. (and I'm sure I've forgotten a couple of other things).

I haven't yet seen a system that prevents stall - just that there is a stick-shaker stall warning.

What I've also noticed is that many accidents (including those unrelated to stall) are caused by human-computer interface problems, where pilots can't understand why the automation is making something happen and overriding their basic manual flying instincts. Same thing with Lion Air disaster. Pilots are forced to become software debuggers to figure out what's happening. Here's an extreme case: imagine faced with so many alerts and still flying an airplane. They even have keyboards !

It is difficult to prevent stall if the primary sensors keep failing or gives conflicting information and the pilots are unable to comprehend or are poorly trained to take the right decision within seconds or couple of minutes.

Poor Pilot training has been cause of many accidents where a minor and perfectly solvable issue had turned into critical situation leading to disaster.

But many of these Aircrash Investigations do not cover many instances where the same instrument , Automation along with good piloting skills have saved a bad situation from getting worse and saved life and there are many dozen such situation.

I have heard from senior instructor from largest airline in India once tell us that Desi Pilots are resorting to Jugad i.e Monkey See Monkey Does instead of relying on Official Pilot Manual.

srin wrote:Pitot tube blockage due to icing seems dependent not just on latitudes but on weather at high altitudes.

In one of the Air France Air Crash investigation which happened due to Pitot Tube Icing and Pilot taking wrong action which lead to crash.

It was mentioned in at High Altitude depending on weather condition the Pitot tube do freeze and Air craft can show incorrect speed , Pilots are advised to stay calm and do nothing and wait for time to pass till the Pitot tube defrezes and returns to normal. The Auto Pilot though gets disengaged and pilot has to take manual control

It appears that almost all the crashes that we are reading about seem to have their genesis in errors in pitot tube and/OR AoA measurements... is there a more reliable instrument (less accurate) that can be switched on for bringing the plane back home in failsafe mode. Perhaps there can be an AI assistant that use simulators to train for such cases and provide the pilot an effective diagnoses for such emergency conditions...

Received via whatsapp. Not sure about accuracy. Apologies this is posted before:

Death by Computer

157 people recently died in a tragic crash. The crew and passengers of Ethiopian Airline Flight # ET302 on board a brand new Boeing 737 MAX 8 never had a chance.

The less than three months old plane had a new software in it. They called it MCAS or Maneuvering Characteristics Augmentations System. MCAS was a system that didn't exist in any of the Boeing 737's before. However, when they built the 737 MAX version, in layman's term, they built the plane with a larger and more efficient engine.

However, this larger engine, which delivered a further 14% fuel efficiency had to be fitted further forward under the low wings of the 737. This potentially may cause the plane to stall. Stalling is bad. It is basically when a plane stops flying and starts falling.

In order to avoid this, Boeing installed the new MCAS software. This software is designed to tell the plane to move its nose down to increase its speed and avoid it from stalling.

So here comes the problem.

In the computer world, we have this term called GIGO. The old school fella's will know this. Yes. Garbage In, Garbage Out.

The problem based on the findings so far is this.

On the plane there is a sensor called the Alpha Vane which measures the Angle of Attack (AOA) of the plane. It looks like a small little wing, and they have two of it, one on the pilot side, and the other on the co-pilot's.

The sensor's job is to tell the computer the angle the plane is flying at. And if the AOA of the plane is too high, this will result in the plane stalling. Typically the AOA is below 15 to 20 degrees, and the new MCAS software will push the plane's nose down if it thinks that the AOA is too high.

Now.

With this flight the Alpha Vane sensor measuring the AOA on the Captain's side was reported to be faulty. So they changed it. That fault was reported from the equally harrowing flight from Bali to Jakarta.

On the fateful final flight, the plane which arrived from Bali the night before, had the sensor changed, and then it took off in the morning.

No one knew what was really wrong with the plane, or about the new MCAS software. No one. Not the maintenance folks, and in fact not even the pilot. He apparently wasn't trained on it yet.

So they flew the plane.

And once in the air, the faulty sensor told the computer that the plane is stalling. The computer then, without the pilot ever knowing pushed the nose of the plane down further, while the pilot was trying to raise the plane.

In this battle between the pilot and the computer, the computer won. And the pilot, the crew, and the passengers lost and they died. The plane was too low, and the pilot didn't have enough air to raise the plane and fly it.

The computer literally flew the plane into the ocean.

A few weeks later, Boeing issued an update on the plane, and informed that should the plane have an issue with it's AOA sensors, one of the way to stop the computer was to switch it off!

Apparently 189 lives could have been saved, had the pilot knew about the software, and flipped a switch to turn it off.

A switch!

A single simple switch was the difference between life and death.

I am still fuming thinking about this. A switch!

Computers are really going to be the end of us all, because while a man makes mistakes, to really, really screw up; you need a computer!

overspeed implies/indicates that a critical flight parameter was exceeded placing the aircraft in imminent danger.

Such was not the case.

Thanks Chetak saar. Overspeed was mentioned in the news article I read but they may have got the nomenclature wrong. While the aircraft may not have actually overspeeded in terms of its airframe limit at that altitude but what I guess they may be talking about is the aircraft exceeding the limit of 250 kias set on all flights flying under 10000 ft.

overspeed implies/indicates that a critical flight parameter was exceeded placing the aircraft in imminent danger.

Such was not the case.

Thanks Chetak saar. Overspeed was mentioned in the news article I read but they may have got the nomenclature wrong. While the aircraft may not have actually overspeeded in terms of its airframe limit at that altitude but what I guess they may be talking about is the aircraft exceeding the limit of 250 kias set on all flights flying under 10000 ft.

nachiket saar,

for that phase of the flight, the speed may have been "abnormal" as per normal practice and accepted norms but not exceeding VNE which would have been the limit before the likely onset of structural issues.

Performance based navigation (PBN) departure and arrivals are driving more automation and autopilot approach nowadays. There is a rush for systemization of airspace primarily to fit in more aircraft in terminal airspace (and noise mitigation, emission controls etc) without necessarily increasing ground based infrastructure like runways and reduce pilot workload. Aircraft manufacturers are therefore continuously upgrading the on-board flight management system (FMS) and associated airplane flight systems and features like 4D path tracking. In case of Ethiopian I don't think the airspace is optimized yet for PBN but the 737 max FMS aircraft systems are definitely modern.

Dubai has implemented continuous descent arrival regime so has Heathrow T5. London airspace has launched a modernisation programme for eliminating holding stacks altogether with predetermined departure letterboxes and arrival gateways in the sky for continuous arrival and departures.

- A unstable design due to new engines that causes the nose to pitch up due to changes to its aerodynamics.- MCAS software that implemented as a poor work around to fix this flaw and to receive a quick certification.- MCAS relying on single sensor and airlines have to pay extra for indicators to show a AoA sensor conflict.- MCAS being far more aggressive in combating the stall than documented to FAA ( this could be bad for FAA for failing to catch it and Boeing).- Boeing not properly alerting pilots on it and insisting no additional training is requiring in order to compete against Airbus.- Boeing failure to quickly ground all 737 max and ensure pilots are aware of this and know how to handle it after Lion air crash.

So far the airlines has been lucky any serious accident of P&W engine has been limited to single engine failure .......GTF engine has been having issues perhaps due to the complication of GTF itself while the much similar approach of LEAP has been reliable so far.

Beyond the reliability beyond the reliability issue with Geared Turbofan Engine , I think Maintaining them would be another challenge

Chao's request comes amid reports US authorities have also launched a criminal probe into the certification of the top-selling jet, which has been grounded around the world.

Nearly 350 people have died aboard 737 MAX 8 aircraft in crashes less than five months apart in Indonesia and Ethiopia, with the most recent occurring March 10 outside Addis Ababa.

Preliminary reports have identified similarities in between the two crashes, in which the planes plunged to earth shortly after takeoff.

In a Tuesday memo to Transportation Inspector General Calvin Scovel, Chao said Boeing had requested an "amended type certification" for the 737 MAX 8 in January 2012, which it received in March 2017.

Chao said she was requesting the audit to develop "an objective and detailed factual history" of the process of certifying the aircraft.

The memo confirmed earlier media reporting that such a probe was underway.

An inspector general's office is an independent oversight body within a US federal agency that conducts audits but can also refer matters it discovers to law enforcement authorities.

Investigators so far are reportedly focusing on the Maneuvering Characteristics Augmentation System, or MCAS, implicated in October's Indonesian crash.

Ethiopian authorities and France's Bureau of Investigation and Analysis (BEA), which examined data from the most recent crash, say they have found "clear similarities" between the Ethiopian and Lion Air crashes.

Boeing said Sunday it was finalising a software update and pilot training tied to the MCAS.

Elaine Chao and her staff flew on a Southwest Airlines 737 Max 8 from Austin, Texas to Washington, D.C. hours after the Transportation Secretary was emphatic in saying her department will ground Max planes if it's determined they are not safe to fly.

"The department and the FAA will not hesitate to take immediate and appropriate action," Chao said, as airlines and governments around the world shutting down Boeing 737 Max airplanes.

With airlines and governments around the world shutting down Boeing 737 Max airplanes after a second deadly crash of the aircraft, U.S. Secretary of Transportation Elaine Chao is not only resisting the calls to ground the plane, she even flew one of the planes back to Washington Tuesday afternoon.

Chao and her staff flew on a Southwest Airlines 737 Max 8 from Austin, Texas to Washington, D.C. just hours after the Transportation Secretary was emphatic in saying her department will ground Max planes if it's determined they are not safe to fly.

"The department and the FAA will not hesitate to take immediate and appropriate action," Chao said.

Ethiopian Airlines Flight 302 crashed shortly after takeoff from Addis Ababa on Sunday, killing all 157 people on board. It came less than five months after a Lion Air Boeing 737 Max 8 went down in Indonesia last October — none of the 157 people on board survived.

Chao's comments were echoed by acting FAA administrator Daniel Elwell who issued a statement late Tuesday afternoon defending the FAA decision not to order airlines to stop flying the newest Boeing commercial airplanes.

"Thus far, our review shows no systemic performance issues and provides no basis to order grounding the aircraft. Nor have other civil aviation authorities provided data to us that would warrant action," Elwell said in a release from the FAA.

"In the course of our urgent review of data on the Ethiopian Airlines Flight 302 crash, if any issues affecting the continued airworthiness of the aircraft are identified, the FAA will take immediate and appropriate action."

While Elwell and his boss are waiting to see data to convince them the 737 Max planes should not fly, more than thirty airlines, several countries and the European Union have decided to ground the planes.

The decisions have created a perception for some that regulators in Washington, D.C. and three U.S. airlines that fly the Max are being stubborn by continuing to fly the Max. Southwest and American Airlines, who fly the 737 Max 8, and United Airlines, which flies the 737 Max 9, have all said they have no plans to take the plane out of service.

— Correction: This story has been corrected to reflect that Southwest Airlines, American Airlines and United Airlines have no plans to take the Boeing Max aircraft out of service.